Bringing ET Home

Using weather stations and evapotranspiration-based irrigation in the residential setting.

 By Robert E. Reaves

While weather station-based technology has become widely used in agricultural and golf course irrigation scheduling throughout the United States, its use in the residential and commercial landscape markets continues to be very limited. This is likely to change as water utilities begin to take advantage of new technologies that link weather stations, computers and pagers with irrigation controllers -- eliminating water waste and replacing it with evatranspiration(ET)-based irrigation management. For the irrigation industry and the end user, it means a paradigm shift in the way we irrigate our landscapes.
The timing could not be better. With more restrictions around the country that limit landscape irrigation during times of drought, the irrigation industry often finds itself at odds with state and local water authorities. Even the best in educational programs and watering restrictions have not resulted in sustained water savings.

"The green industry can't wait another five or 10 years to make changes in the way we irrigate landscapes," said Tom Ash, horticulturist and water conservation manager for the Irvine Ranch Water District (IRWD), Orange County, Calif.

"As an example, California tried to push through legislation (AB2734) that scared the daylights out of the green industry. The legislation mandated landscapes must use no more than 0.6 of local ET. Had our state budget not been in trouble, it probably would have passed."

The solution is to have automated, real-time, ET-based watering schedules generated by credible weather station data. However, there are hindrances that could stall implementing ET controller technology across the country. Ask any irrigation equipment manufacturer and they'll probably voice concern that water utilities won't embrace the technology. Likewise, water utilities are concerned that technolgies on the market now won't be there tomorrow.

There are also other variables to consider, too. "In some communities the price of water is so cheap that retrofitting for savings is not cost effective over the short term," Ash said. "In other cases it may be that no accessible and reliable weather stations exist. Or, that plant information (Kc) is not known for a wide range of plants. Another roadblock is that people feel uncomfortable about someone having control over their irrigation times."

IRWD STUDIED AVAILABLE TECHNOLOGY

After spending three years and more than $1 million on ET controller pilot studies, IRWD knows what works and why it works. "At least seven different companies have visited our agency to show us their ET controller technology," Ash revealed.

Unfortunately, Ash said the majority of ET controller technologies seem to use the same approach. "They set a high average schedule and adjust time up or down based on the weather. From our studies and working with the landscape industry, this approach may or may not work," Ash said.

IRWD eventually selected the Weather Trak ET controller, manufactured by Network Services, Petaluma, Calif. The controller delivers real-time ET directly to a home or landscape and it can schedule many more start times than typical controllers -- very useful in areas with steep slopes.

The Weather Trak calculates a watering schedule based on site-specific variables for each individual valve -- sprinkler type, soil type, plant type, precipitation rate, slope, station relation on a slope, sun or shade and root depth. "This means we can maximize (not generalize) water savings at any given site. Our first extensive study showed we saved 85 percent of the potential water to be saved in a 40-home test," Ash said. Similar results were seen at other pilot studies throughout the West. The results of pilot studies at IRWD have been impressive:

  • 16 percent average reduction in landscape water use (volunteer participants were not necessarily the highest water users);
  • Participants liked the convenience of never having to set or change a schedule;
  • 39 out of 40 claimed their landscape looked as good or better than before the study;
  • 85 percent of the participants saw water bills go down;
  • 85 percent of the potential overwatering was saved.
"In general, we expect to see 25,000 to 35,000 residential controllers installed in our district over the next 10 years," Ash predicted. IRWD is currently trying to get a handle on how many commercial controllers exist in its service area so it might target them if or when an appropriate central control, ET-based system becomes available.

Ash believes it is essential that technology, like that used by Weather Trak, be made widely available.

Local weather station networks send data through phone lines or the Internet to a central computer located at Network Services Corp. The company uses a software program to store and process ET information. Next, ET information is sent to Weather Trak controllers at individual residences via pager/satellite technology on a weekly and as-needed basis (e.g. rain or sudden temperature changes.) Once the controller receives the ET information, software inside the controller along with specific site data sets a schedule.

Either Network Services Corp. or a water utility bills $4 per month to the end user. Current retail cost for a 12-station controller is $195, "but [costs] are much lower for water districts when they buy in quantities," said Mike Marian, chief technology officer, Network Services. "Our projected selling price within three years is less than $100. We will be introducing a commercial version with up to 48 stations. The target price for a 24station controller is about $800 to $900, which will provide central control features."

WEATHER REACH

Another product that delivers real-time ET technology is the Weather Reach system, developed by Irrisoft, Inc., a subsidiary of Campbell Scientific. A local entity (such as a water district) operates the Weather Reach server, which collects data from local weather stations. The data is broadcast, via paging, to Weather Reach receivers, which calculates ET and interfaces with any brand of controller. Weather Reach brings cost-effective ET-based technology to the commercial and residential landscape market that was previously only available through central control systems such as Rain Bird's Maxicom®.

With the Weather Reach system, ET information gets to the controller through an accessory, called a Weather Reach receiver, a device that simply connects to an existing controller. "We aren't a controller manufacturer," said Steven Moore, president, Irrisoft, Inc., North Logan, Utah. "We don't care whose controller you have. You have that choice. All we are doing is getting the ET data to the controller."

The Weather Reach receiver hasseveral interfaces that can be used to automatically adjust irrigation based on ET.

Three major elements comprise the system: automated weather stations (local and weather station networks); Weather Reach software (Windows® based application) and; Weather Reach receivers (will work with any type or brand of controller).

There are already weather station networks in existence, and Moore says it will not be difficult for a weather service provider to offer Weather Reach on a statewide, regional or local basis.

In addition to connecting to a Motorola Flex® paging service (such as Metrocall) to broadcast weather data to Weather Reach receivers on an hourly basis, the software automatically updates ET and weather data to a Web site. Reports and graphs can be generated as well.

"We are actively talking with the major irrigation controller manufacturers and, in the future, hope to supply controller manufacturers with a plug-in card that would operate through a serial port or RS-232 connection," Moore revealed. He said the receiver card would have all the necessary information needed to provide ET and weather data to the controller.

"We will be focusing on the water districts to access weather stations to collect the data," Moore said. "The server outputs data to a Web site for anyone to access, but also works with the paging service provider that in turns broadcasts the data."

The Weather Reach receiver built-in pager receiver displays weather data and calculates an ET value using the new standardized ET equation with a short grass reference (ET.).

"Because we are broadcasting weather data hourly, we can also interrupt irrigation in the event of rain, wind or freeze-hence there would be no need for a rain, wind or freeze sensor," he added.

However, the Weather Reach receivers still accepts a tipping bucket rain sensor if one is needed.

MORE INNOVATION TO COME

In addition to the technologies discussed above, other companies throughout the United States have products that can deliver ET-based irrigation to residential and commercial landscapes.

One example is Sensible Technologies, Inc., a Houston, Texas-based firm that manufactures various environmental instrumentation and weather station software.

"We license our Met Manager(TM) software to other weather station manufacturers. This software calculates ET data using the new standardized ASCE Penman-Monteith reference equation," said Jim McCabe, president. "Using our software, data from a weather station is retrieved by dial-up or direct connection to a PC. The data can then ultimately be linked to an irrigation controller through pager or other technology.

"The purpose of an irrigation control system is to supply supplemental irrigation water when rainfall is not sufficient to maintain the landscape," he added. "Using ET or soil moisture sensor-based irrigation, you balance out the unpredictability of nature. The goal is to maintain a functional and healthy turf and landscape without wasting water."

Unfortunately, McCabe said technology will not fix an irrigation system with poor design or maintenance. "With less water applied, poor irrigation systems will be much more obvious," he said. This in turn should spawnincreasedbusinessfor good irrigation design, maintenance and management.

CONSIDERATIONS

If you're considering using ET-based technology, just how many weather stations a re needed to accurately depict a region? "A rule of thumb is one weather station for every 10 to 30 square miles, with the number of microclimates in a region an important factor," said Neal Israelsen, marketing manager, Campbell Scientific, Inc.

"Weather stations are a piece of the pie, but the most important thing is what they do with the raw data after they retrieve it," commented John Mascoe, sales manager, North America, Adcon Telemetry, Boca Raton, Fla.

Adcon Telemetry manufactures weather stations that are self-contained and completely solar powered for roughly $4,000 for a basic system with a datalogger.

The cost of weather stations is coming down, making it financially possible to increase the number of weather stations in a region. As an example, Campbell Scientific is rolling out some less expensive stations that will provide ET.

"Some neighborhood covenants in New Mexico are requiring that irrigation systems be controlled by a weather station," Israelsen said.

"With a less expensive unit, you'll be able to provide the basics without the higher cost of a standard unit."

With weather stations and new technologies as the foundation of science-based irrigation, the irrigation industry and water utilities now have the tools to decrease over watering in landscapes.

These new technologies will likely foster long-term partnerships between the irrigation industry and the water industry.